Mars rover poised to touch the surface of the planet

Robotic probe to travel different route off lander

NASA's Spirit rover has completed what the agency calls a "reverse robotic origami," unfolding itself from its flight configuration in preparation for rolling off the lander about midnight Tuesday, much earlier than engineers had predicted just a day ago.

The rover "now stands at full height, and all six wheels are in their final position and ready to drive," said Jennifer Trosper, mission manager at the Jet Propulsion Laboratory in Pasadena, Calif.

The 4-foot-11-inch rover was folded into a compact form so it would fit into the tetrahedron-shaped lander. Unfolding it on Mars was "the most complex sequence of deployments that has ever been done on a robotic spacecraft," said Chris Voorhees, a mechanical systems engineer who devised the maneuver.

To allow the rover to stand up, 12 pyrotechnic devices had to fire, nine motorized mechanisms had to work, and six structural latches had to be engaged, he said. Everything went perfectly, and the rover "is asleep right now and resting on all sixes," he said.

Late yesterday evening, engineers planned to move the instrument arm from its folded flight position to make it ready for travel on the surface. The team will then fire a pyrotechnic device to sever the last cable connecting the rover to the lander, readying Spirit for roll-off.

At that point, Trosper said, "The lander becomes space debris."

The rover will then spend the better part of tomorrow night pivoting 120 degrees to the right on the lander so it can drive off on a secondary ramp. The primary ramp, which would have allowed it to exit by driving straight ahead, is partially blocked by one of the collapsed air bags that cushioned the raft's landing Jan. 3.

Mission engineers tried a simulated roll-off in their "sandbox" laboratory in Pasadena on Friday and concluded that there was a small chance that the rover's solar panels would brush against the bag if it attempted to drive straight forward. "That's not really a place we want to be in," Trosper said. "We don't want to get the solar panels caught on an air bag."

Trosper said Spirit had transmitted more than 200 megabits of data back to Earth overnight Friday, "10 times more than Pathfinder had the capability to do."